At this current moment in time, Edit History information is not something that is retrievable through our API.I do not know of any plans for this to be implemented into our API, but hopefully in the future this becomes available.

The response includes an array of XEditHistory entities where X is the entity type (in the case above, the PlacementEditHistory). Within the EditHistoryEntity you will also find a fieldChanges array which includes the fields being changed as well as their old and new values.